There is known a semiconductor package in which a semiconductor chip (semiconductor element) is covered (sealed) with a resin-made sealing material. The sealing material for the semiconductor package is produced by molding a resin composition, for example, with a transfer molding method.
A process for producing the resin composition includes a mixing process of a resin composition (a composition) including plural kinds of pulverized materials. Each of the pulverized materials has a different specific gravity. For example, the mixing process of the resin composition is performed by a mixing device, such as a high speed mixer, a Lodige mixer, a henschel mixer or the like, which rotates a rotating blade at high speed (for example, see patent document 1). The above mixing devices for high speed agitation include a container and a rotating blade rotatably provided in the container of the mixing device. The resin composition is mixed by rotating the rotating blade in a state that the resin composition is stored in the container of the mixing device.
In the conventional mixing device such as described above, pulverized resin compositions is mixed by rotating the rotating blade at high speed. Therefore, there is a case in that the rotating blade scratches an inner surface of the container. As a result, the conventional mixing device suffers from a problem in that metallic foreign substances (foreign metals) are mixed into the resin composition, which leads to a short circuit and so forth when the semiconductor chip is sealed by the resin composition produced using the conventional mixing device.
For this reason, it is preferable to use a vibration type mixing device, such as a paint shaker and so forth, which mixes the resin composition by vibrating the container in which the resin composition is stored. This makes it possible to prevent (inhibit) the metallic foreign substances from being mixed into the resin composition during mixing.
However, in case of using the paint shaker, there is a problem in that it takes a long time to mix the resin composition.
Patent document 1: JP 2003-105094A